1. Field of the Invention
The present invention relates to a relief mode of a redundant memory in a semiconductor device, and in particular, to a system in which a defective cell in a chip is self-recoverable.
2. Related Art
There has been proposed a method for extracting information to avoid a defect existing in a memory through the operation of a test circuit built in a chip and for fusing down a nonvolatile element by the use of the information (see, for example, Japanese Unexamined Patent Application Publication No. 6-84393).
With large scale integration of a system LSI, the capacity and the number of memories mounted in a chip are increased. Moreover, the number of redundant memories that are mounted in the chip and can be relieved is also increased. However, in the related art disclosed in, for example, Japanese Patent Application No. 2005-155511, the number of redundant memories corresponds one-to-one to the number of relief processing portions, and thus as the number of redundant memories increases, the number of the relief processing portions also increases by the same number. Hence, the chip area is on the increase.
Moreover, in the foregoing related art, relief information storage portions included in the respective detect relief portions are serially connected to each other and relief information outputted from the test circuit is stored in the respective relief information storage portions by a shift operation. This makes longer the time required to transfer the relief information in proportion to the number of the defect relief portions.
Furthermore, in a case where the program operation of the electric fuses is performed on the basis of the information stored in the relief storage portions, when the electric fuses are fused down simultaneously in parallel, an IR drop and the like have an effect on a circuit operation, and hence the electric fuses are serially fused down on the basis of the structure in which the electric fuses are serially connected to each other. This makes longer the time required to fuse down the electric fuses in proportion to the number of the defect relief portions.